1. Field of Invention
This invention pertains to digital modems used for exchanging digital data over communication lines.
2. Description of the Prior Art
It has become common practice to use voice-grade channels to transmit data at relatively high rates, such as 4800 b/sec. However, often these channels, characteristics of which are usually beyond the control of end users, are degraded for various reasons so that the rate at which data is transmitted must be reduced in order to maintain an acceptable data error rate. However most modems used, until now, had external controls for switching data rates so that a degradation in channel resulted in an interruption of the exchange of data until the respective receivers could be reset manually to the new data rate. Obviously it would be very advantageous if the receivers of the modems could adjust automatically to the data rates of signals being received.